.. index:: ScaLAPACK
.. _ScaLAPACK:

ScaLAPACK
=========

Description
-----------

ScaLAPACK is a library of high-performance linear algebra routines for parallel distributed memory machines (think parallel LAPACK).

User instructions
-----------------

ScaLAPACK is available via the modules system.  To add it to your environment run:

.. code-block:: bash

    $ module load scalapack/2.0.2

A relevant OpenMPI module must also be loaded.  ScaLAPACK is trickier to use than LAPACK but extensive documentation is available on the `netlib website <http://www.netlib.org/scalapack/>`_.

To link ScaLAPACK, add '-lscalapack' to the link command.  Note that a LAPACK implementation must also be linked (e.g. :ref:`MKL <Intel suite>` or :ref:`LAPACK`).

The :ref:`MKL <Intel suite>` also contains an (optimised) implementation of ScaLAPACK.

Source
------

http://www.netlib.org/scalapack/

License
-------

Modified BSD license.

Admin notes
-----------

.. code-block:: bash

    # Intel version
    ml intel openmpi lapack
    CMAKE_PREFIX_PATH=$OPENMPI_ROOT CC=icc CXX=icpc cmake ../scalapack-2.0.2 -DCMAKE_INSTALL_PREFIX=/common/debian/9.1/MPI/intel/2017.4/openmpi/2.1/scalapack/scalapack-2.0.2 -DBUILD_TESTING=ON -DBLAS_LIBRARIES:STRING=-lblas -DLAPACK_LIBRARIES:STRING=-llapack
    make
    make test

    # GCC version
    ml purge
    ml gcc openmpi lapack
    CMAKE_PREFIX_PATH=$OPENMPI_ROOT cmake ../scalapack-2.0.2 -DCMAKE_INSTALL_PREFIX=/common/debian/9.1/MPI/gcc/6.3/openmpi/2.1/scalapack/scalapack-2.0.2 -DBUILD_TESTING=ON -DBLAS_LIBRARIES:STRING=-lblas -DLAPACK_LIBRARIES:STRING=-llapack
    make
    make test

BLAS and LAPACK implementations are required to compile the library but these need not be the ones linked to when compiling applications.  For simplicity I chose the netlib reference implementations.

The resultant library (lib/libscalapack.a) can then be just copied to the appropriate directory on the NFS server.